1. Field of the Invention
The present invention relates to a resin-made fuel inlet pipe to be used in a fuel transport piping from a filler opening to a fuel tank in a vehicle such as an automobile and a method of producing the pipe, and more specifically, to a resin-made fuel inlet pipe formed by integrating a filler neck pipe, an inlet tube, and a filler hose, and a method of producing the pipe.
2. Description of the Related Art
A metal piping (inlet pipe) has been conventionally used on the fueling side of a fuel transport piping from a filler opening to a fuel tank in an automobile from the viewpoint of collision safety (impact resistance). A product obtained by connecting a resin- or rubber-made filler hose to the metal piping has been used by being attached to the fuel tank. In recent years, however, investigation has been conducted on a resin-made hose instead of the metal piping in association with a demand for a reduction in weight of the piping for an automobile.
For example, the following resin-made fuel filler tube for an automobile (Japanese Laid-open Patent Application No. 11-48800) has been proposed as a resin-made hose. The fuel filler tube is of a two-layer construction having two kinds of layers obtained by using a modified polyethylene resin in the outer layer of the main body of the tube, and any one of a polyamide-based resin, and ethylene vinyl alcohol and an elastomer thereof each having gas barrier property in the inner layer thereof.
However, the tube described in Japanese Laid-open Patent Application No. 11-48800 has the following drawback. Since the inner layer and the outer layer are integrally joined to each other by fusion, the occurrence of a crack in the inner layer at the time of collision causes a crack in the outer layer fused to the inner layer as well, with the result that fuel leaks to the outside. On the other hand, when an attempt is made to increase the thickness of the resin hose to provide the hose with impact resistance comparable to that of the metal piping, its volume also increases owing to the increased thickness of the hose, which is contrary to the demand for weight reduction.